Process and apparatus for the continuous replacement of the catalyst in a moving-bed unit

Abstract

A process for the simultaneous replacement of a first catalyst by a second catalyst which first catalyst is circulating as a moving bed of solid particles in a hydrocarbon treating unit, which unit comprises at least one processing reactor. The first catalyst is withdrawn downstream of the reactor, or of each reactor, in the direction of catalyst circulation. The second catalyst is simultaneously injected upstream of the reactor or of each reactor. The bulk density of the material withdrawn downstream of the reactor, or of each reactor, is measured continuously. The withdrawal of the first catalyst and the injection of the second catalyst into the reactor concerned are interrupted when the bulk density so measured is equal to that of the second catalyst.

What is claimed is: 
     
       1. A process for continuously replacing a first catalyst of solid particles circulating as a moving bed with particles of a second catalyst in a hydrocarbon treating unit having at least one processing reactor and treatment occurring in the unit, without the necessity of interrupting treatment occurring in such unit, said process comprising withdrawing the first catalyst downstream of each reactor relative to the direction of catalyst circulation;   injecting simultaneously the second catalyst upstream of each reactor at essentially the same volume flow rate as the rate of withdrawal of the first catalyst, with said second catalyst particles having an effectively measurable difference in bulk density from that of the first catalyst;   measuring bulk density continuously or at effective intervals to sense the bulk density of the catalyst withdrawn downstream of each reactor sufficiently to detect the occurrence of a change in bulk density, and   interrupting the withdrawal of the first catalyst and the injection of the second catalyst when the bulk density of the withdrawn catalyst has been sensed to be different from that of the first catalyst and becomes equal to that of the second catalyst.   
     
     
       2. A process for continuously replacing a first catalyst of solid particles circulating as a moving bed with particles of a second catalyst in a hydrocarbon treating unit having at least one processing reactor, without the necessity of interrupting treatment occurring in such unit, said process comprising withdrawing solid particles, initially composed of the first catalyst, downstream of each reactor relative to the direction of catalyst circulation;   injecting simultaneously the second catalyst upstream of each reactor at essentially the same volume flow rate as the rate of withdrawal of the first catalyst, with said injecting including injecting a quantity of particles of a third solid substance prior to the injection of the second catalyst, said third substance having a bulk density sufficiently sensibly different from that of the first and second catalysts and said injecting of said third substance being in an amount such that the third substance effectively serves as a marker between the first and second catalysts;   measuring bulk density continuously or at effective intervals to sense bulk density of the solid particles withdrawn downstream of each reactor sufficiently to detect the occurrence of a change in bulk density, and   interrupting the withdrawal of the solid particles and the injection of the second catalyst when the bulk density of the withdrawn solid particles has been sensed to be different from that of the first catalyst and becomes equal to that of the marker.   
     
     
       3. The process as defined in claim 2, wherein the bulk density of at least one of the second catalyst and of the third substance differs from that of the first catalyst by more than 1 percent. 
     
     
       4. The process as defined in claim 2, wherein the bulk density of at least one of the second catalyst and of the third substance differs from that of the first catalyst by from about 2.5 to 25 percent. 
     
     
       5. The process as defined in claim 1 applied to a hydrocarbon treating unit having several reactors, which process comprises simultaneously replacing the first catalyst in such reactors in a synchronized manner with a second catalyst, and comparing the bulk densities of the catalyst particles withdrawn simultaneously downstream of each of the reactors and regulating the second-catalyst feed rate to each of these reactors and the withdrawal rate from each of these reactors so as to maintain substantially equal measured densities. 
     
     
       6. The process as defined in claim 2, wherein the first and second catalysts have substantially the same bulk density, and wherein the volume of the third solid substance injected represents approximately from 1 to 2 percent by weight of that of the first catalyst. 
     
     
       7. The process as defined in claim 1, wherein variations with time of the bulk density of the material withdrawn from the reactor are represented graphically. 
     
     
       8. The process defined in claim 1, wherein the first and second catalysts have sensibly different densities such that the second is inherently marked as different from the first with respect to their respective bulk densities. 
     
     
       9. The process as defined in claim 1, wherein said treatment in the hydrocarbon treating unit is chosen from the group consisting of reforming, cracking, isomerization and hydrotreatment of vacuum distillation residues. 
     
     
       10. A process for continuously replacing a first catalyst of solid particles circulating as a moving bed with particles of a second catalyst in a hydrocarbon treating unit having at least one processing reactor and treatment occurring in the unit, without interrupting the treatment occurring in such unit, said process comprising withdrawing the first catalyst downstream of each reactor relative to the direction of catalyst circulation;   injecting simultaneously the second catalyst upstream of each reactor at essentially the same volume flow rate as the rate of withdrawal of the first catalyst, with said second catalyst particles having a bulk density sensibly different from that of the first catalyst;   measuring continuously or at effective intervals the bulk density of the catalyst withdrawn downstream of each reactor sufficiently to detect such sensible change in bulk density, and   interrupting the withdrawal of the first catalyst and the injection of the second catalyst when the measured bulk density of the withdrawn catalyst after having been measured as different from that of the second catalyst becomes equal to that of the second catalyst.   
     
     
       11. A process for continuously replacing a first catalyst of solid particles circulating as a moving bed with particles of a second catalyst in a hydrocarbon treating unit having at least one processing reactor and treatment occurring in the unit, without interrupting the treatment occurring in such unit, said process comprising withdrawing solid particles, initially composed of the first catalyst, downstream of each reactor relative to the direction of catalyst circulation;   injecting simultaneously the second catalyst upstream of each reactor at essentially the same volume flow rate as the rate of withdrawal of the first catalyst, with said injecting including injecting a quantity of particles of a third solid substance prior to the injection of the second catalyst, said third substance having a bulk density sufficiently sensibly different from that of the first and second catalysts and said injecting of said third substance being in an amount such that the third substance effectively serves as a marker between the first and second catalysts;   measuring bulk density continuously or at effective intervals to sense bulk density of the solid particles withdrawn downstream of each reactor sufficiently to detect the occurrence of a change in bulk density, and   interrupting the withdrawal of the solid particles and the injection of the second catalyst when the bulk density of the withdrawn solid particles has been sensed to be different from that of the first catalyst and becomes equal to that of the marker.   
     
     
       12. The process as defined in claim 10, wherein the bulk density of at least one of the second catalyst and of the third substance differs from that of the first catalyst by more than 1 percent. 
     
     
       13. The process as defined in claim 10 applied to a hydrocarbon treating unit having several reactors, which process comprises simultaneously replacing the first catalyst in such reactors in a synchronized manner with a second catalyst, and comparing the bulk densities of the catalyst particles withdrawn simultaneously downstream of each of the reactors and regulating the second-catalyst feed rate to each of these reactors and the withdrawal rate from each of these reactors so as to maintain substantially equal measured densities. 
     
     
       14. The process as defined in claim 11, wherein the first and second catalysts have substantially the same bulk density, and wherein the volume of the third solid substance injected represents approximately from 1 to 2 percent by weight of that of the first catalyst.